Gain/Offset

Gain/Offset
The Gain/Offset I/O multiplies a signal with a constant gain factor and adds a constant offset. Both an input offset and an output offset are available. An input offset can be automatically removed using the Neutralize input offset action.

Typical application: converting sensor values

A typical application of the Gain/Offset I/O is converting sensor output signals. Suppose a pressure sensor has the following characteristic:

The graph shows that when the pressure is 0 Pa, the output signal equals 0.85 V. To convert the 0.85 V to a pressure of 0 Pa, the Input offset must be set to -0.85.

The graphs also shows that when the pressure varies from 0 to 220 MPa, the output voltage changes from 0.85 V to 3.93 V. This is used to calculate the required Gain:

Note that the gain can be calculated by the Multi Channel oscilloscope software by entering ( 220e6 - 0 ) / ( 3.93 - 0.85 ) directly in the input dialog. Instead of e6, also M can be used.

Set the Unit of the Gain/Offset I/O to 'Pa'.

Properties and actions

To control the behavior of the Gain/Offset I/O, several properties and actions are available. These can be accessed through a popup menu which is shown when the I/O is right clicked.

Gain

The Gain property determines how much the input signal is multiplied. A value smaller than 1 reduces the signal magnitude. Several default values are available and it is also possible to enter a user defined value.

Hint: To invert a source, you can use a Gain/Offset I/O with a gain of -1.

Input offset

The Input offset is applied to the input signal before the gain is applied. Several default values are available and it is also possible to enter a user defined value.

Neutralize

When an input signal contains an offset, it can be removed automatically by using the Neutralize action. This action uses the current data in the I/O to determine the offset and stores the inverted value in the Input offset property to remove the offset. Each time new data arrives at the Gain/Offset I/O, this determined offset value is used.

Auto neutralize

The Auto neutralize action also removes the offset of data in the Gain/Offset I/O, but it uses the next data that will arrive in the I/O. Once the data has arrived, it will determine the offset and store the inverted value in the Input offset property to remove the offset. The action is then disabled again and each time new data arrives at the Gain/Offset I/O, this determined offset value is used.

This action is useful when a measurement setup with a Gain/Offset I/O that is used to compensate an offset in the signal is saved to disk, in a TPS file. Before saving the TPS file, the Auto neutralize action is enabled and then the TPS file is saved. When the TPS file is loaded again in a later situation, and the first measurement is performed, the auto neutralize action will determine the correct offset value and neutralize it.

Output offset

The Output offset is applied to the input signal after the gain is applied. Several default values are available and it is also possible to enter a user defined value.

Spectrum to density

When the source of the Gain/Offset I/O is a spectrum, you can use the Spectrum to density setting to convert a magnitude spectrum into a density spectrum. For example if the unit of the source spectrum is V, the output unit will become V/Hz.

Common properties and actions

Related information

Add/Subtract

The Add/Subtract I/O adds or subtracts data of two or more sources.

Multiply/Divide

The Multiply/Divide I/O multiplies or divides data of two ore more sources.

Sqrt

The SQRT I/O calculates the square root of each sample of the source's data.

ABS

The ABS I/O takes the absolute value of each sample of the source's data.

Differentiate

The Differentiate I/O differentiates the source's data.

Integrate

The Integrate I/O integrates its source's data.

Logarithm

The Logarithm I/O calculates the logarithm of the source's data.

FFT

The FFT I/O is used for spectral analysis of a signal using a Fast Fourier Transformation